1. Field of the Invention
The present invention relates to a storage device that consumes less power by stop of supply of power for a short time, and a signal processing circuit including the storage device. The present invention also relates to methods for driving the storage device and the signal processing circuit. Moreover, the present invention relates to an electronic device including the signal processing circuit.
2. Description of the Related Art
Circuit operation has been complicated with higher integration and larger scale of semiconductor integrated circuits. In addition, the leakage current of transistors is increased with miniaturization of semiconductor integrated circuit processes, and unnecessary power is consumed by the leakage current even while a semiconductor integrated circuit does not operate.
In view of the above, there has been proposed a method in which supply of power to a semiconductor integrated circuit is temporarily stopped in a period during which the semiconductor integrated circuit does not operate. For example, Patent Document 1 discloses a method in which a nonvolatile storage device is disposed around a volatile storage device such as a register or a cache memory so that data in the register, the cache memory, or the like is temporarily stored in the nonvolatile storage device.
In the case where supply of power is stopped for a long time with the above method, data in the volatile storage device can be prevented from being lost by being transferred to an external storage device such as a hard disk or flash memory before supply of power is stopped.